This project will investigate immunoregulation of the T cell-mediated immune response of contact hypersensitivity to 1-fluoro-2,4-dinitro-benzene (DNFB) in mice. Tolerance induced by the i.v. injection of hapten-modified lymphoid cells (DNP-LC) is mediated by two separable pathways - clone inhibition and antigen-specific suppressor T cells (Ts). The DNP-modified membrane determinants on DNP-LC involved in the induction of these two pathways will be investigated. The contribution of these two pathways on maintenance of the tolerant state will be studied. Genetic restrictions on both Ts induction and expression will be determined using DNP-LC of both high and low hapten density for tolerance induction. The role of the spleen as a depot of Ts precursors will also be studied. Finally, the effects of i.v. tolerization with DNP-LC on the development of anti-hapten-modified self cytotoxic cells will be examined.